The synthesis of immunoglobulin in vitro will be studied in human peripheral blood lymphocytes after short-term culture with pokeweed mitogen. Secreted Ig will be measured by isotope radioincorporation and immunoprecipitation. The effect of prednisolone treatment on Ig synthesis and secretion will be analyzed at different levels of pokeweed mitogen. Cell separation experiments and irradiation will be used to examine the contribution of each cell type. The relationship between steroid sensitive cells in normal peripheral blood and steroid-sensitive suppressor cells in iummnodeficiency will be studied.